What is the process of phagocytosis (descriptive version)
Take a deep breath!
The process that results in phagocytosis is characterized by three interrelated steps: adherence and diapedesis, tissue invasion by chemotaxis, and phagocytosis. A, Adherence, margination, diapedesis, and chemotaxis. The primary phagocyte in the blood is the neutrophil, which usually moves freely within the vessel (1). At sites of inflammation, the neutrophil progressively develops increased adherence to the endothelium, leading to accumulation along the vessel wall (margination or pavementing) (2). At sites of endothelial cell retraction the neutrophil exits the blood by means of diapedesis (3)Chemotaxis. In the tissues, the neutrophil detects chemotactic factor gradients through surface receptors (1) and migrates towards higher concentrations of the factors (2). The high concentration of chemotactic factors at the site of inflammation immobilizes the neutrophil (3)B, Specific receptors for recognition and attachment. C, Phagocytosis. Opsonized microorganisms bind to the surface of a phagocyte through specific receptors (1). The microorganism is ingested into a phagocytic vacuole, or phagosome (2). Lysosomes fuse with the phagosome, resulting in the formation of a phagolysosome (3). During this process the microorganism is exposed to products of the lysosomes, including a variety of enzymes and products of the hexose-monophosphate shunt (e.g., H2O2, O2−). The microorganism is killed and digested (4)Ab, Antibody; AbR, antibody receptor; C3b, complement component C3b; C3bR, complement C3b receptor; PAMP, pathogen-associated molecular pattern; PRR, pattern recognition receptor.